96 900 fit an 02?

A friend bought a 96 ZXI. Went to dmv and numbers wrong. Can’t register it. I told him easier to find a nice ski with bad motor than to try to deal with the number issue. He found an 02 STS 900. Engine looks the same. Will he have to do anything with the ignition-charging-security system? Or will it go right in with only carb interchange issues. Thanks.